The space agency celebrates its 55th birthday on Monday. The National Aeronautics and Space Administration was founded by president Dwight Eisenhower in 1958 with the passing of the National Aeronautics and Space Act (the agency would start operations in October of 1958). In the last five-and-a-half decades the men, women, animals and robots of NASA have explored our solar system, given us unforgettable glimpses of the planets and our interstellar neighbours and taken those first careful steps off Earth. Here's a look back at some of the most memorable moments from NASA's history

The Voyager and Pioneer space probes have now left our solar system or are at its outer borders. Voyager 1 is about 11 1/2 billion miles away from Earth. Both probes carry a golden LP with messages and sounds from our planet. If you listen to Ann Druyan, Carl Sagan's widow, talk about the record you'll also realize that some of the nerds at NASA are the biggest romantics around.

A photo of Jupiter from 1979, taken by the Voyager 1 probe. (Getty Images)

4. You also put a giant telescope into space so we can get a better look